Cystic fibrosis is the most common lethal autosomal recessive disorder in the white population. The disease is characterized by (1) chronic pulmonary disease, (2) deficient exocrine pancreatic function, and (3) other complications of inspissated mucus in a number of organs, including the small intestine, the liver, and the reproductive tract. It results from abnormal electrolyte transport caused by impaired function of the chloride channel of epithelial cells. The pulmonary symptoms of CF begin with cough, which eventually becomes productive of large amounts of tenacious and purulent sputum. Episodes of infectious bronchitis and bronchopneumonia become progressively more frequent, and eventually shortness of breath develops. Respiratory failure and the cardiac complications of pulmonary hypertension (cor pulmonale) are late sequelae. The most common organisms that infect the respiratory tract in CF are Staphylococcus and Pseudomonas species. As the disease advances, Pseudomonas may be the only organism cultured from the lung. In fact, the recovery of Pseudomonas sp., particularly the mucoid variety, from the lungs of a child with chronic pulmonary disease is virtually diagnostic of CF.Diagnosis: Cystic fibrosis